Methods and devices detect a first lateral measure of an edge of a belt loop supported by rollers within an apparatus using a first sensor to find an amount of misalignment of the edge of the belt loop relative to a known alignment position. In use, the rider is seated on the seat of the flying ski and towed by the watercraft. The invention may include the steps of generating mass spectra data from samples taken from a population that responds to a treatment of a disease, generating mass spectra data from samples taken from a population that does not respond to the same treatment of the disease, and comparing the two sets of data. In a first embodiment, the energy-absorbing device defines a second crush surface positioned to directly interface with the edge surface of the vehicle rail in the event of an impact. This step is performed while supplying a cleaning gas containing hydrogen fluoride into the reaction chamber, and forming a first atmosphere within the reaction chamber, which allows water to be present as a liquid film. The sense amplifier circuit includes of a first pre-charge circuit, a second pre-charge circuit, a bias circuit, an enable circuit, a current mirror, a first comparator, a second comparator, a buffer and a counter.